One in 10 older people will likely be abused this year -- that's more than 4 million people.

But in the media and society, elder abuse often goes unnoticed and is underreported.

With the help of a viewer who shared his evidence, a Channel 4 Action News investigation hopes to expose an old problem in Pennsylvania that's expected to get worse with age.

Thomas Spradlin contacted WTAE for help after he captured cellphone video of an elderly woman who was slapped in the back of the head by her daughter at the Glassport Diner.

He turned the video over to the Department of Human Services, but he wanted to make sure they pursued an investigation.

"I just wasn't satisfied with them saying they were going to send an investigator," Spradlin said.

Then he called Channel 4 Action News to help keep tabs on the case.

He said he captured the abuse at the diner several weeks ago after he noticed disturbing behavior.

"I saw her get up once and actually slap her (the elder woman's) hand and was yelling at her because she was lifting a fork to her mouth without food on it, and after that, I started to tape it on my phone. I mean, it was just disgusting," said Spradlin.

During his seven-minute clip, other eyebrow-raising behavior can be seen. You can't hear the pair's conversation, but Spradlin said others wouldn't want too.

"She was saying 'you're (expletive) me off' and I heard 'you stupid (expletive).' Basically, stuff like that, yelling at her like she was a child or something," said Spradlin.

Diner staff members Channel 4 Action News spoke to would not go on camera, but they said the mother has been abused by her daughter at the same table, on and off, for at least 10 years.

Spradlin said there were four other people at the diner. While he regrets not speaking up during the abuse, he did not stay quiet afterwards and filed a report with the county.

Donald Grant, with Allegheny County's Department of Human Services, said elder abuse is on the rise, with the victims age 60 and older. The abuse can take several forms, including neglect, financial exploitation and physical harm. Channel 4 showed him Spradlin's cellphone video.

He would not release details about the investigation, including whether anyone has stopped by the home of the victim. But Grant did say police are investigating possible criminal charges. Grant said most abusers are family members and elderly victims typically don't want the county's help.

"If an older adult does not want our intervention, then we have to walk away," said Grant. "That being said, they have to have the capacity to make that decision."

In the past 20 years, Allegheny County statistics show elder abuse reports more than doubled. In 1993, there were 613 reported county cases; 1,466 in 2003; and 1,517 in 2013.

Despite the uptick in caseload, substantiating the allegations still proves difficult. In fact, 20 years ago, they found just over 33 percent of reports were substantiated compared to just over 24 percent this past year.

"I'd like to see her be arrested and be punished somehow and the mother get some kind of help," said Spradlin.

Spradlin doesn't consider himself a hero for sounding the alarm, but his video does provide a rare piece of evidence: a glimpse at a common problem often brushed under the rug. In the Glassport Diner case, if this victim can and chooses to refuse help, the county says at least they provide hope.

"Maybe the next time they'll say, 'You know what, I'm ready for your help,'" said Grant.

The county attributes the spike in reports to increased awareness and increases in neglect. In substantiated cases, a care plan is developed to reduce or eliminate the risk.

If someone suspects elder abuse, the county recommends speaking up. Also, it's best when callers can provide authorities with details, like the victim's and alleged abuser's names, the time and place of the incident and the victim's mental capacity.